Gasoline solutions containing a scavenger for the oxides of nitrogen

ABSTRACT

The scavenger for oxides of nitrogen to be used in gasoline solutions is ethyl carbamate also called urethane. This compound is not soluble in 100% gasoline but it is soluble in solutions of 90/10 v/v gasoline/ethanol, 90/10 v/v gasoline/methanol and 90/10 v/v gasoline/mixture of ethanol and methanol. A small percentage of water such as 5% by volume can be present in the alcohol so therefore, 190 proof ethanol can be used. The solutions of ethyl carbamate in the above blends of gasoline and alcohol are clear and stable both at room temperature and at sub-freezing temperatures such as −15° C.  
     The concept of this invention is that the ethyl carbamate must first hydrolyze to ethyl alcohol and carbamic acid in the internal combustion engine due to the presence of water vapor. The ethyl alcohol produced combusts and the carbamic acid decomposes to carbon dioxide and ammonia. The ammonia reduces the NOx that had been generated giving nitrogen and water vapor. The late release of ammonia in the exhaust gases when most of the oxygen has been depleted in the combustion of the fuel is the key to the concept of this invention.

REFERENCES CITED

[0001] James M. Valentine, U.S. Pat. No. 5,535,708

[0002] Henry W. Steinmann, U.S. Pat. No. 6,017,368

[0003] Von Harpe, T. et al, (Fuel Tech. GmbH) PCT Int., Appl. WO 92 02,291 (Cl. BOID 53/34) Feb. 20, 1992 [(Chemical Abstracts 117: 55047k (1992)]

[0004] Kulish et al, Energetik 1992, (7), 6-8 (Russian) [(Chemical Abstracts 117: 257192q (1992)]

BACKGROUND

[0005] There are numerous reports in the literature including patent literature that the addition of ammonia to the exhaust gases of the internal combustion engine and also, to flue gases from furnaces, significantly reduces the oxides of nitrogen in the gases. The oxides of nitrogen, abbreviated NO_(x), result from the chemical reaction of nitrogen with oxygen of the air due to the high temperatures of conbustion of the fuel, petroleum based or coal. The temperature is the main factor regarding the formation of NO_(x), the higher the combustion temperature, the greater the amount of the formation of NO_(x).

[0006] When aqueous solutions of urea, cyanuric acid or ammonia are sprayed into the exhaust chamber, the oxides of nitrogen are reduced to nitrogen. In the case of urea or cyanuric acid the mechanism of the reaction involves the formation of ammonia and it is the ammonia that reduces the oxides of nitrogen according to the following chemical equation:

6 NO_(x)+4x NH₃→(2x+3) N₂+6x H₂O

[0007] There are two processes abbreviated SCR and NSCR. The SCR is a selective catalytic reduction and the NSCR is a non-catalytic selective reduction.

[0008] It is not expected that the above reaction is complete in the short reaction time involved with either process but there is a significant reduction in the oxides of nitrogen. For example, Kulish et al reported that the efficiency of NOx removal from power plant flue gases by non-catalytic reduction with urea was 50% at 1050-1100° F. with excess air coefficient of 1.1 and 65-85% at 950-1000° F. with excess air coefficient of 1.25-1.3. Von Harpe et al reported that an aqueous solution of urea heated to 500° F. through a conduit for a time effective to hydrolyze urea to produce products comprising ammonium carbamate, ammonium carbonate, ammonium bicarbonate and ammonia. This paper as well as other papers show that it is the ammomia that is the effective reducing agent for NOx in the exhaust gas systems.

[0009] The fundamental in this invention is to have a precursor to the reducing agent dissolved in the gasoline. The precursor is ethyl carbamate. This compound was found not to be soluble in 100% gasoline but was discovered to be readily soluble in v/v 90/10 gasoline/95% ethanol and also in v/v 90/10 gasoline/methanol or in v/v 90/10 gasoline/mixture of 95% ethanol and methanol. Clear and stable solutions both at room temperature and at sub-freezing temperatures such as −15° C. were obtained.

[0010] During combustion of the gasolune in the engine, the ethyl carbamate readily hydrolyzes to give ethyl alcohol and carbamic acid. The ethyl alcohol combusts to give carbon dioxide and water vapor and the carbamic acid decomposes to give ammonia and carbon dioxide. This late release of ammonia is desirable for the reduction of NOx formed during the combustion stage and at the time when the oxygen content in the gases are at a minimum. Recognize that the reason it is desirable to have the oxygen content of the gases at a minimum is to prevent, or at least, minimize the reverse reaction which is the oxidation of ammonia, usually to nitric oxide, as shown by the following equation:

4 NH₃+5 O₂→4 NO+6 H₂O

BRIEF SUMMARY OF THE INVENTION

[0011] This invention is most useful for gasoline fuels containing ethyl alcohol such as Gasohol. The v/v 90/10 gasoline/95% ethyl alcohol is ideal. For example, 3 grams of ethyl carbamate readily dissolves in a solution of 90 mls of gasoline and 10 mls of denatured ethyl alcohol containing 5% water by volume giving crystal clear solutions both at room temperature and at sub-freezing temperatures such as −15° C. Larger amounts of ethyl carbamate such as 5 grams can be dissolved and the solutions are stable at −15° C. by dissolving a small amount of octanol-1.

[0012] It is important to note that the ethyl alcohol need not be anhydrous and that the practical 95% ethyl alcohol containing 5% water by volume can be readily used.

[0013] Methanol alone or blended with ethyl alcohol can also be readily used. Thus, a stable, crystal clear solution of v/v 90/10 gasoline/methanol containing 4% of ethyl carbamate can be prepared.

[0014] This invention cannot be used with urea as is done in the microemulsion system of Steinmann's U.S. Pat. No. 6,017,368. There is not enough water in the solution to dissolve the urea and one needs the microemulsion system containing sufficient water to dissolve the urea.

DETAILED DESCRIPTION OF THE INVENTION

[0015] Denatured 190 proof ethyl alcohol was used for the experiments. It is comprised of the following for every 100 parts by volume of the alcohol:

[0016] (a) 87% ethyl alcohol

[0017] (b) 5% methanol

[0018] (c) 1% ethyl acetate

[0019] (d) 1% methyl isobutyl ketone

[0020] (e) 1% hydrocarbons

[0021] (f) 5% water

[0022] The calculated specific gravity is 0.800.

[0023] The specific gravity of unleaded gasoline is 0.723.

[0024] Since the denatured alcohol contained 5% water by volume and that 190 proof ethyl alcohol or 95% ethyl alcohol also contains 5% water, it is apparent that 95% ethyl alcohol containing 5% water by volume and without the presence of denaturants can be readily used.

EXAMPLE I

[0025] Three grams of ethyl carbamate were dissolved in 10 mls. of the denatured ethyl alcohol. This solution was added to 90 mls. of unleaded gasoline. A crystal clear solution resulted.

[0026] The solution was put in the freezer at −15° C. overnight and then examined. It was still crystal clear without any precipitation of ethyl carbamate. The solution was left in the freezer for a week and re-examined. It was still crystal clear. The weight composition of the solution is shown in Table 1. TABLE 1 Weight Composition of Gasoline Solution of EXAMPLE 1 Unleaded Gasoline, % 85.54% Ethyl Alcohol, % 9.02 Denaturants, % 0.84 Water, % 0.66 Ethyl Carbamate, % 3.94

EXAMPLE II

[0027] Four grams of ethyl carbamate were dissolved in 10 mls. of the denatured ethyl alcohol. This solution was added to 90 mls. of unleaded gasoline. A crystal clear solution resulted.

[0028] The solution was put in the freezer overnight and then examined. It was still crystal clear. It was left in the freezer and then examined a week later. A slight amount of ethyl carbamate crystals had precipitated which shows that 4 grams of ethyl carbamate is borderline and therefore, not acceptable.

[0029] The weight composition is shown in Table 2. TABLE 2 Weight Composition of the Gasoline Solution of EXAMPLE II Unleaded Gasoline, % 84.43 Ethyl Alcohol, % 8.90 Denaturants, % 0.83 Water, % 0.65 Ethyl Carbamate, % 5.19

EXAMPLE III

[0030] Four grams of ethyl carbamate were dissolved in 10 mls. of methanol. To this solution were added 90 mls. of unleaded gasoline. A crystal clear solution resulted.

[0031] The solution was put in the freezer at −15° C. for a week and examined periodically. It remained crystal clear without any precipitation of a solid material.

[0032] The weight composition of the solution of EXAMPLE III is shown in Table 3. TABLE 3 Weight Composition of the Gasoline Solution of EXAMPLE III Unleaded Gasoline, % 84.52 Metanol, % 10.29 Ethyl Carbamate, % 5.19

[0033] Since this experiment is an improvement over EXAMPLE II in which a slight amount of a solid precipitate occurred, the reason could be that when methanol is used the system is anhydrous and that ethyl carbamate is more soluble in an anhydrous system.

EXAMPLE IV

[0034] A weight of four grams of ethyl carbamate was dissolved in 10 mls. of the denatured ethyl alcohol and 2 mls. of octanol-1 to give a clear solution. This solution was added to 90 mls. of unleaded gasoline. A crystal clear solution resulted.

[0035] The solution was placed in the freezer at −15° C. for a week and examined periodically. It remained crystal clear which shows that the addition of a small amount of octanol-1 improved the stability at −15° C. compared to the solution of EXAMPLE II. The weight composition of the solution is shown in Table 4. TABLE 4 Weight Composition of the Gasoline Solution of EXAMPLE IV Unleaded gasoline, % 82.65 Ethyl Alcohol, % 8.71 Denaturants, % 0.81 Water, % 0.64 Octanol-1, % 2.11 Ethyl carbamate, % 5.08

EXAMPLE V

[0036] Five grams of ethyl carbamate were dissolved in 10 mls. of 95% denatured ethyl alcohol and 2 mls. of octanol-1. To this solution was added 90 mls. of unleaded gasoline. A crystal clear solution resulted. This was placed in the freezer at −15° C. for a week and examined periodically. It remained clear without any precipitation of solid material. The weight composition is shown in Table 5. TABLE 5 Weight Composition of the Gasoline Solution of EXAMPLE V Unleaded Gasoline, % 81.61 Ethyl Alcohol, % 8.61 Denaturants, % 0.80 Water, % 0.63 Octanol-1, % 2.08 Ethyl Carbamate, % 6.27

[0037] The conclusion is that with the addition of a small amount of octanol-1, even more ethyl carbamate NOx scavenger can be dissolved in the solution than shown in EXAMPLE IV.

EXAMPLE VI

[0038] Five grams of ethyl carbamate were dissolved in 15 mls. of 95% denatured ethyl alcohol. When 90 mls. of unleaded gasoline were added, a crystal clear solution resulted. The solution was placed in the freezer at −15° C. for one week and examined periodically. It remained crystal clear. This shows that increasing the ethyl alcohol rather than adding a small amount of octanol-1 is effective in dissolving more ethyl carbamate. The weight composition is shown in Table 6. TABLE 6 Weight Composition of the Gasoline Solution of EXAMPLE VI Unleaded Gasoline, % 79.29 Ethyl Alcohol, % 12.54 Denaturants, % 1.17 Water, % 0.91 Ethyl Carbamate, % 6.09

EXAMPLE VII

[0039] Five grams of ethyl carbamate were added to 15 mls. of methanol to give a clear solution. To this solution were added 90 mls. of unleaded gasoline. A crystal clear solution resulted. This was placed in the freezer for one week and examined periodically. It remained crystal clear without any precipitation of a solid phase.

[0040] The weight composition of this solution is shown in Table 7. TABLE 7 Weight Composition of the Gasoline Solution of EXAMPLE VII Unleaded Gasoline, % 79.40 Methanol, % 14.50 Ethyl Carbamate, % 6.10

EXAMPLE VIII

[0041] A weight of 3.5 grams of ethyl carbamate was dissolved in a solution of 5 mls. of 95% denatured ethyl alcohol and 5 mls. of methanol. To this solution were added 90 mls. of unleaded gasoline. A crystal clear solution resulted.

[0042] The solution was placed in a freezer at −15° C. for one week and examined periodically. It remained crystal clear without any precipitation of a solid phase.

[0043] The weight percentages of the components of the solution of EXAMPLE VIII are shown in Table 8. TABLE 8 Weight Composition of the Gasoline Solution of EXAMPLE VIII Unleaded Gasoline, % 85.03 Ethyl Alcohol, % 4.48 Methyl Alcohol, % 5.17 Denaturants, % 0.42 Water, % 0.33 Ethyl Carbamate, % 4.57 

I claim:
 1. A composition of matter consisting of the ethyl carbamate NOx scavenger dissolved in unleaded gasoline containing an aliphatic alcohol made by blending at low shear a solution of ethyl carbamate in the alcohol with unleaded gasoline resulting in a clear, low viscosity solution that is stable and remains clear without any solid phase precipitaion over a wide range of temperatures including sub-freezing temperatures such as −15° C.
 2. Claim 1 in which the aliphatic alcohol is 95% denatured ethyl alcohol.
 3. Claim 1 in which the aliphatic alcohol is methanol.
 4. Claim 1 in which the aliphatic alcohol consists of a solution blend of 95% denatured ethyl alcohol and methanol.
 5. Claim 1 in which the aliphatic alcohol consists of a solution blend of 95% denatured ethyl alcohol and octanol-1.
 6. Claims 1 and 2 in which the composition is v/v 90/10 unleaded gasoline/95% denatured ethyl alcohol containing 0.1 to 4.0% ethyl carbamate by weight.
 7. Claims 1 and 2 in which the composition is v/v 85/15 unleaded gasoline/95% denatured ethyl alcohol containing 0.1 to 5.0% ethyl carbamate by weight.
 8. Claims 1 and 3 in which the composition is v/v 90/10 unleaded gasoline/methanol containing 0.1 to 5.2% ethyl carbamate by weight.
 9. Claims 1 and 3 in which the composition is v/v 85/15 unleaded gasoline/methanol containing 0.1 to 6.1% ethyl carbamate by weight.
 10. Claims 1 and 4 in which the composition is v/v 90/5/5 unleaded gasoline/95% denatured ethyl alcohol/methanol containing 0.1 to 4.6% ethyl carbamate by weight.
 11. Claims 1 and 5 in which the composition is v/v88.2/9.8/2.0 unleaded gasoline/95% denatured ethyl alcohol/octanol-1 containing from 0.1 to 6.3% ethyl carbamate. 